"Lavage" means 'washing'. To lavage a joint means to wash out any blood, fluid or loose debris from inside the joint space. Arthroscopic lavage is generally combined with arthroscopic debridement, where fronds of joint material or degenerative tissue are removed using a combination of injected fluid and a small vacuum, i.e. both washing (rinsing) and sucking. 'Arthroscopic' means that this is done using a tiny incision at the joint, where a thin arthroscope is pushed into the joint to inspect the structures. Excessive growth of irritated synovial membrane causes it to increase its surface area by buckling into fronds, and the fronds may become inflamed and pour destructive enzymes into the joint space, causing joint swelling and joint surface destruction...